Modification of hexagonal boron nitride by thermal treatment.

The catalytic activity of hexagonal boron nitride (hBN) is not yet well understood, but it seems to be related to hBN hydroxylated sites. A good understanding of those sites and how they are produced is a key step to reveal the true nature of hBN catalytic activity. Here, we report a set of thermal treatments to produce a diversity of hydroxylated sites, as well as a method to remove the boric acid produced by hBN decomposition. We found that some of the boric acid dehydrates on the surface of hBN to produce a borated hBN (hBNO) characterized by an FTIR peat at 1090 cm−1 and an XRD shift due to the variation in the planar distance. We also showed that when characterizing the thermal treated hBN, the storage of the sample changed the borate's hydration degree and modified both the XRD pattern and the FTIR spectrum. When stored in a humid environment, boric acid peaks are visible, but they are not present if samples are stored in a dry place. The methods established here are a solid basis for the manufacture, purification and characterization of hBN by thermal treatments, showing how the process can be designed to generate various functional groups on its surface. [ABSTRACT FROM AUTHOR]